Silurocypridina calva Perrier, Vannier, and Siveter, 2011

Legiot, Nicolas, 2019, Silurian myodocope ostracods from Poland, Acta Palaeontologica Polonica 64 (2), pp. 379-397 : 392-393

Silurocypridina calva Perrier, Vannier, and Siveter, 2011

Fig. 2L .

1899 Cypridina sp. aff. C. Tosterupi Mob; Canavari 1899: 152.

1900 Cypridina tyrrhenica n.f.; Canavari 1900: 204, pl. 26: 10–12 (specimens I91, I92).

1987 “Cypridinid” sp.; Siveter et al. 1987: 801, pl. 85: 1, 2, 4, 5.

1987 “Cypridinid” sp. nov. B; Siveter et al. 1987: 805, pl. 87: 2–4.

1990 “Cypridinid” sp. nov.; Siveter and Vannier 1990: 64, text-fig. 23 (number 6).

1991 “Cypridinid” sp.; Siveter et al. 1991: 157, pl. 1: 3.

1992 “Cypridinid”-like myodocopes; Vannier and Abe 1992: 489, 509, pl. 2: 2, text-fig. 1.

1992 “Cypridinid” sp.; Vannier and Abe 1992: 494, text-fig. 6I, J.

2000 “Cypridinid” Genus B, sp. B of Siveter et al. 1987; Kornicker and Sohn 2000: 21.

2003 “Cypridinid” sp. nov. B of Siveter et al.; Gabbott et al. 2003: 157, text-fig. 4B.

2009 “ Cypridinid ” gen. and sp. nov.; Gnoli et al. 2009: 1, text-figs. 12–22.

2011 Silurocypridina calva sp. nov.; Perrier et al. 2011: pl. 5: 1–9, 12–14, text-figs. 6, 8A, 10.

2012 Silurocypridina calva Perrier, Vannier and Siveter, 2011 ; Perrier 2012: text-fig. 7F.

2019 Silurocypridina calva Perrier et al., 2011 ; Perrier et al. 2019: pl. 17: 1–5, 8–11.

Holotype: A three-dimensionally preserved left valve ( LPB 18926 ); Perrier et al. (2011: pl. 5: 8, 9).

Type locality: Les Chevrolières, near St Denis-d’Orques, Sarthe, France ( Perrier et al. 2011).

Type horizon: Le Val Formation ; the type horizon is within the upper part of the Ludlow Series or lower part of the Pridoli Series, and currently cannot be further resolved .

Material.—Tens of valves, from two localities (Widełki and

Niestachów), Holy Cross Mountain, Poland, Ludlow Series, Silurian.

Measurements (in mm).—Size range: L = 2, H = 2.1 ( ZPAL O.63/32) to L = 4, H = 3.15 ( ZPAL O.63/33). Holotype: L = 2.38, H = 1.48 ( LPB 18926). L/H ratio and adductor muscle position for seven specimens from two localities ( Fig. 3).

Description.—Valve dome-like, with sub-ovoid lateral outline; hinge short. Rostrum well developed, is about 10–15% of valve length, protrudes distinctly forward beyond anteroventral margin of valve. Rostral incisure well developed, rounded to angular in lateral outline. Adductor muscle scar is small, subcentral, crescent-shaped convex anteriorly. Valves smooth. During ontogeny valve shape changes from almost circular to sub-ovoid.

Remarks.— Silurocypridina calva displays considerable variation in valve outline and shape of the rostrum. Besides material from France and the Czech Republic other, less well preserved and limited material from Sardinia ( Cypridina tyrrhenica Canavari, 1900 ; types in Museo de Storia Natural e del Territorio, Calci) is possibly conspecific. One very large incomplete specimen from Widełki( ZPAL O.63/12, Fig. 2M ) shares some characteristics with “cypridinid” ostracods (i.e., valve outline and rostrum); however, its size (L = 15.25, H = 10.75 mm) and the absence of a crescent shape muscle scar are not consistent with the genus Silurocypridina . Either this specimen represents a deformed fossil belonging to a completely different group or it may belong to a new group of fossil “cypridinids”.

Stratigraphic and geographic range.—Ludlow Series, Holy Cross Mountains, Poland. Also known from the Silurian of the Czech Republic, France, England, Wales, and possibly Sardinia (see Perrier et al. 2011, 2019).

Figures

Fig. 2. Selected Silurian myodocope species, Holy Cross Mountains, Poland; Ludlow Series, Silurian. A, B. Bolbozoe anomala Barrande, 1872. A. ZPAL O.63/1, incomplete left valve. B. ZPAL O.63/2, juvenile right valve. C. Bolbozoe psittaca Perrier, Siveter, Williams, and Palmer, 2019, ZPAL O.63/3, left valve. D, E. Parabolbozoe bohemica (Barrande, 1872). D. ZPAL O.63/4, juvenile left valve. E. ZPAL O.63/5, right valve. F. Richteria migrans (Barrande, 1872), ZPAL O.63/6, left valve. G, H. Nudator angiportatus Perrier, Siveter, Williams, and Palmer, 2019. G. ZPAL O.63/7, juvenile left valve. H. ZPAL O.63/8, left valve. I, J. Nudator inflatus Perrier, Siveter, Williams, and Palmer, 2019. I. ZPAL O.63/9, right valve showing post-mortem diagenetic structures. J. ZPAL O.63/9, right valve. K. Silurocypridina retroreticulata Perrier, Vannier, and Siveter, 2011, ZPAL O.63/10, incomplete right valve. L. Silurocypridina calva Perrier, Vannier, and Siveter, 2011, ZPAL O.63/11, right valve. M. Cypridinid?, ZPAL O.63/12, right valve. All light photographs in lateral view. A–H, J, M, silicone casts of external moulds; I, K, L, internal moulds. Scale bars 1 mm, except M 2 mm.